"In the five months since the UK's Brexit vote, the only things which are clear are that their policy is a shambles and that it is already causing real damage on this island," the Irish Opposition leader warned.

"Brexit is not something which is happening in two years, it is happening now."

Calling for an urgent national plan in Dublin to deal with the "slow-motion crash", Mr Martin has also demanded the EU suspend normal state aid rules for worst-hit Irish industries.

During an address to Sean Moylan, an IRA commandant in the 1920s and later government minister at Kiskeam in Co Cork, Mr Martin also lashed out at the UK, accusing the nation of "backward-looking nationalism" over Brexit decision.

Lord Kilclooney lambasted what he termed "the usual hysteria and anti-British rhetoric" which he said "we in Northern Ireland always expect from Fianna Fáil - especially since it is now challenged by Sinn Fein!"

However he then turned to agree with Mr Martin.

"Michael Martin, is right to declare that Brexit is causing real damage in the Republic," he said.

"Likewise, its Prime Minister, Enda Kenny, has already confirmed that the Republic will suffer more from Brexit than any of the other 26 EU nations.

"With exports already down 4%; mushroom plants closing; Irish beef prices falling; thousands of shoppers from the Republic of Ireland rushing up to Northern Ireland; and a decline in tourist numbers from the UK; urgent action by the Government in Dublin is now required."

Lord Kilclooney said it is time that "economic reality prevailed".

"Within these Isles - I do not use the term British Isles - we have a shared history; sport; culture; language; and, above all, trade," he said.

"That trading arrangement is now under challenge. It is time that economic reality prevailed.

"Assuming the Republic re-joining the UK or leaving the EU is not on the political agenda - yet - there must be a united effort in Dublin; Belfast; and London to achieve a special status for the Republic following Brexit in order to avoid the clouds of economic despair which Michael Martin correctly identifies."

Earlier this year the UK voted by 51.9% to 48.1% to leave the EU.

However there were regional variations in the result with Northern Ireland voting by a majority to remain in the EU.

A group of MLAs and also victims campaigner Raymond McCord have taken court cases challenging the result.